The studies proposed in this application are concerned with the replication and expression of viral DNA in cells infected with herpes simplex virus (HSV). The studies concerning viral DNA replication are designed to both characterize and map the cis functions involved in the initiation of viral DNA synthesis, and in the processing and packaging of the progeny viral DNA into mature virions. Specifically, we propose to analyze the replication and propagation of both defective and non-defective HSV DNA by using both biochemical and genetic approaches. The studies concerning the expression of HSV DNA concentrate mostly on the pattern of viral transcription and polypeptide synthesis in cells infected with various populations of defective herpes simplex viruses.